Droplet generation

Claim 1

A method of forming spherical, smooth and uniform microapsules containing living tissue or cells, which comprises: forming a suspension of living tissue or cells in a physiologically-compatible medium containing a water-soluble substance which can be reversibly gelled to provide a temporary protective environment for the living tissue or cells, extruding said suspension downwardly from a source at a first location comprising an axially downwardly directed electroconductive needle, charging the extruded material with a charge of one polarity, establishing a charge of opposite polarity at a second location spaced vertically below said first location, providing a difference in voltage between the first location and second location cyclically in pulses of a magnitude from about 1 to about 25 kv at a frequency of about 10 to about 100 sec-1 for a pulse duration of about 1 to about 6 m. sec. to effect continuous production of droplets from the extruded material and to draw the droplets so-formed towards said second location, collecting said droplets in a recipient medium which is a hardening solution which reacts with said water-soluble substance and form discrete, spherical microcapsules from each of said droplets of diameter less than about 700 microns, and subsequently forming a permanent biocompatible semi-permeable membrane having a negatively-charged outer surface about each of said microcapsules which forms a core of the resulting spherical, smooth and uniform microcapsules, said membrane permitting nutrients and oxygen to flow to the core material and metabolic products to flow therefrom while retaining the core material within the microcapsule, said membrane comprising ionically-interacted biocompatible materials and having a thickness about 4 to about 6 microns, said resulting microcapsules being suitable for cardiovascular injection.

Claim 2

A method of forming spherical, smooth and uniform microapsules containing living tissue or cells, which comprises: forming a suspension of living tissue or cells in a physiologically-compatible medium containing a water-soluble substance which can be reversibly gelled to provide a temporary protective environment for the living tissue or cells, extruding said suspension downwardly from a source at a first location comprising an axially downwardly directed electroconductive needle, charging the extruded material with a charge of one polarity, establishing a charge of opposite polarity at a second location spaced vertically below said first location, providing a difference in voltage between the first location and second location cyclically in pulses of a magnitude from about 1 to about 25 kv at a frequency of about 10 to about 100 sec-1 for a pulse duration of about 1 to about 6 m. sec. to effect continuous production of droplets from the extruded material and to draw the droplets so-formed towards said second location, collecting said droplets in a recipient medium which is a hardening solution which reacts with said water-soluble substance and form discrete, spherical microcapsules from each of said droplets of diameter less than about 700 microns, and subsequently forming a permanent biocompatible semi-permeable membrane having a negatively-charged outer surface about each of said microcapsules which forms a core of the resulting spherical, smooth and uniform microcapsules, said membrane permitting nutrients and oxygen to flow to the core material and metabolic products to flow therefrom while retaining the core material within the microcapsule, said membrane comprising ionically-interacted biocompatible materials and having a thickness about 4 to about 6 microns, said resulting microcapsules being suitable for cardiovascular injection.